Recently, the team of the University of Science and Technology of China proposed a new energy utilization method that can capture and utilize the hot and cold energy of the sun and deep space 24 hours a day, providing a new way for the efficient use of solar and space energy.
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Most of the energy used in human society comes from solar radiation, and the waste heat after the energy is used can be dissipated into low-temperature space through mid-infrared thermal radiation. From a thermodynamic point of view, the sun and space are the ultimate heat and ultimate cold source of Earth's energy cycle. Photothermal conversion obtains high-temperature thermal energy through the direct use of solar radiation. Sky radiation refrigeration can directly emit surface energy in the form of infrared radiation to low-temperature space through the atmospheric window to obtain low-temperature cooling capacity and realize the ultra-long-distance direct utilization of deep space and low temperature.
However, the current photothermal conversion and sky radiation cooling both rely on static spectral selective coatings, and both processes have infrared spectral conflicts, and previous technologies have been the use of a single target and a single function.
This time, Pei Gang, professor of the Anhui Provincial Key Laboratory of Comprehensive Solar Thermal Utilization of Solar Energy and The National Synchrotron Radiation Laboratory and the College of Nuclear Science and Technology, joint research team of the University of Science and Technology of China, innovatively proposed the use of spectral adaptive regulation mechanism to decouple the solar heat source and space cold source in time, breaking through the current single utilization of solar heat source and space cold source.
The aforementioned team proposed an energy utilization method, which takes the sun (about 6000 K Kelvin degrees) and space (about 3K Kelvin degrees) as the heat source and cold source respectively, and cleverly uses the spectral adaptive intelligent coating to solve the spectral conflict between the photothermal conversion process and the radiation refrigeration process, and finally realizes the capture and utilization of cold and heat energy 24 hours a day. The results were published in the Proceedings of the National Academy of Sciences (PNAS) on April 19.
Image courtesy of The Proceedings of the National Academy of Sciences (PNAS)
The team developed a multilayer membrane spectral-selective adaptive coating based on vanadium dioxide phase change materials. The coating is in a metallic state under the irradiation of the sun during the day, and the overall solar absorption rate of the coating is 0.89, and the infrared emissivity is only 0.25, which is characterized by photothermal absorption. At night without irradiation, the coating is insulated and has high emissivity in the atmospheric window band and low emissivity in the rest of the mid-infrared band, which is characterized by radiative cooling.
The measured results show that the surface temperature of the aforementioned device can be 170 °C (degrees Celsius) higher than the ambient temperature during the day and 20 °C lower than the ambient temperature at night, which has the adaptive functions of daytime photothermal conversion and nighttime radiation cooling. The device can operate 24 hours a day, greatly improving the overall efficiency of hot and cold energy capture. This finding provides a completely new approach to energy capture and efficient utilization based on solar heat sources and space cold sources.
The picture is from the University of Science and Technology of China
Pei Gang's team has been working on research in the field of solar energy and sky radiation refrigeration. On the one hand, they developed the theory of comprehensive utilization of solar energy and sky radiation refrigeration, and proposed the spectral coupling principle of a variety of comprehensive utilization processes, introducing optical thin films and photonic crystal structures to achieve spectral selectivity under multi-cut wavelengths of coatings; on the other hand, they deeply cultivated in daytime sky radiation refrigeration technology, and realized the passive refrigeration effect under solar irradiation conditions through the development of high-performance spectral selective coatings, the development of low heat loss systems and the optimization of radiation transmission paths. These technologies can be widely used in building energy efficiency, photovoltaic cooling, thermoelectric conversion, and deep space exploration. Zou Chongwen's team has long been engaged in the preparation of vanadium dioxide phase change films, phase change regulation research, and the application of infrared/terahertz devices, smart coatings, laser protection and uncooled infrared detectors.
The first authors of the paper are Ao Xianze, Zhao Bin and Li Bowen of the National Synchrotron Radiation Laboratory of the College of Engineering of the University of Science and Technology of China, and the corresponding authors are Pei Gang and Zou Chongwen. The above-mentioned research has been supported by projects and institutions such as the National Natural Science Foundation of China, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the special funds for basic scientific research business expenses of central universities, and the Multi-energy Complementary Energy Conversion Research Center. The relevant test work has been supported by the Micro-nano Center of the University of Science and Technology of China, the Soft X-ray Magnetic Circular Dicolor Experimental Station (BL12B) of the National Laboratory for Synchrotron Radiation, and the Infrared Spectroscopy and Microscopy Imaging Experimental Station (BL01B).